Safety brake



2 Sheets-Sheet l J. R.`MCGIFFERT ET AL SAFETY .BRAKE Filed Feb. 15. 1932HII lll llll Oct. 9, 1934.

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00L 9, 1934, J. R. MGu-'FERT ET AL 1,976,406

SAFETY BRAKE Filed Feb. l5. 1932 2 Sheets-Sheet 2 Patented Oct. 9, 1934UNITED STATES PATENT OFFC SAFETY BRAKE John R. McGiffert and Ola L.Berby, Duluth, Minn., assignors to Clyde Iron Works, Duluth, Minn., acorporation of Maine Application February 15, 1932, Serial No. 592,868

11 Claims. (Cl. 18S-82) This invention relates to safety brakes whichthe operating lever into normal position or when may be used forhoisting mechanism to provide it is accidentally released into normalposition. a safety appliance therefor, or for other similar Thus, weprovide a means of safety for the means where it is desirable to providea safety hoisting mechanism or other mechanism where 5. braking meanswith a differential brake, such as this safety means is applied, whichwith its cushis used on hoisting mechanisms. f ioning means provides avery desirable safety A feature resides in providing a safety brakebraking means for hoisting mechanisms or other with cushioning means,whereby any shock of Similar devices, where a safety brake is desirable.

l the braking means, when suddenly applied, or t is of primaryimportance to provide a cushioni@ applied in a manner to engage the drumor the ing means which acts to absorb sudden shock or rotating member tobrake the same, will be abgrabbing of the safety brake and whichco-opersorbed in the cushioning'me'ans, rather than diates to overcomethe detrimental features of recting the shock of the braking to ahoisting braking means where braking strains are sudden- I or supportingcable or to the other mechanism ly applied. With this safety brakemeans, undeb where this safety brake is applied. sirable shocks andstrains are relieved from the 70y This safety brake includes means forapplying operating parts, making the same more safe to a brake to abrake drum or to other braking protect lives and overcoming undue wearon the means, in theV case of an emergency, where, operating parts.should the operator release the lever which op- This safety brake meanswhen applied to a 0 erates the regular braking means for the drumhoisting mechanism, overcomes accidental drop- 75 and which may alsocontrol the safety brake, then ping Of the Suspended lOld and PIOVideS ameans this safety brake means is automatically applied wherein thesafety brake operates instantly with and the cushioning meansincorporated therein the releasing of the manual controlling lever willabsorb the shock or force which would be which operates'the regularbrake for the hoist ordinarily directed to the member being engaged andprovides that added feature of cushioning 30.

by the safety brake. Therefore, with this safety the application of thesafety brake to give a brake means, even if the operator was carelessmore desirable braking means for hoists and other and released thecontrol lever, the safety brake mechanism, where a brake of thischaracter is would be automatically applied without damage desired.

0 or danger, or should the operator suddenly die, These features,together with other details, ob- 85 the safety brake would be appliedwithout undue jects, and applications of the safety brake means strainupon the operating parts including the will be more fully and clearlyset forth throughcable, brake drum and mechanism. out the'specicationand claims.

In hoisting mechanisms, theL cable which op- In the drawings forming apart of this specicrates the elevator carriage or which is operatedcation: 90

to raise and lower loads is wound upon the op- Figure 1 is a plan Viewof a hoisting mechaerating spool or spools and a brake is providednism'showing a pair of operating spools for cawhich engages against thebrake drum for holdbles with my safety brake means applied thereto. ingthe spool in a set position or in braking the Figure 2 is a sideelevation of the hoisting same in the operation of the hoistingmechanism. mechanism illustrated in Figure l. 95 This safety brake meansis applicable to the Figure 3 is a diagrammatic side view of the spoolor spools of the hoisting mechanism, and safety brake mechanism shown inFigures 1 may be operated by the same lever which controls and 2. theregular brake for stopping the spool. When Figure 4 is a diagrammaticside view of a dethis safety brake means is applied to a hoisting tailshowing another form of the safety brake 100 mechanism and the samelever which controls the mechanism. regular brake operates the safetybrake means, Figure 5 is a side View of still another form of we providea means for causing the safety brake the safety brake means showing adetail thereof. to automatically engage upon the release of the In thedrawings, we have illustrated the safety lever which operates theregular brake, so that brake A as applied to a hoisting mechanism B. 105

if this lever is accidentally released into normal The hoistingmechanism B is mounted upon a position or is released into this positionin the frame consisting of side frame members l0, end operation of thehoisting mechanism by the opframe members 11 and cross supports 12 and13. erator, the safety brake mechanism will come into Winding spools 14and 15 are supported on the operation simultaneously with the movementof frame of the hoisting mechanism B in a manner 110 which is notdisclosed in the drawings, but which is common in the art. Gear wheels16 and 17 are mounted co-axially with the spools 14 and 15 respectively.Each of the gear wheels 16 and 17 is in engagement with a pinion 18,mounted upon the shaft 19 of the pulley 20. The pulley 20 is driventhrough the flexible driving means 22. The winding spools 14 and 15 aredriven by the gear wheels 16 and 17, when the levers 23 and 24respectively are rotated. Rotation of t. -e handle levers 23 and 24 actsthrough thrust screws to bring the ends of the spools 14 and 15 adjacentthe gear wheels 16 and 17 in contact with friction blocks carried bythese gear wheels. This construction is common in the art and thedetails of construction have not been illustrated in the drawings.

Each of the spools 14 and 15 is provided with a brake drum upon eitherside thereof. The. spoolA 14 is provided with a brake drum 25 which actsas a service brake drum and a drum 26 which acts. as the saety brakedrum. The spool isl provided in a similar manner with a drum 27 whichacts as a service brake drum and a drum 26 which acts as the safetybrake drum. Brake bands 29 and 36 are provided for the service brakedrums and 27 and brake bands 32 and 33 are provided for the safety brakedrums 26 and 28. Each of the various brake bands is preferably formed intwo parts with an adjusting means 34 interposed between these two parts.

As may be seen in Figure 2 of the drawings, the brake. band 29A of thespool 14 is pivotally secured at one end at 35 to a plate 36 which isrigidly secured tothe frame of the hoisting mechanism B. The. other endof the service brake band 29 is pivotally secured at 37 to the arm 38mounted for rotation therewith. The foot lever is also clamped upon theshaft 39 and acts to rotate this shaft when the foot lever 46 isdepressed. It may be seen that a downward pressure upon the foot lever40 will act to rotate theY arm 38 in a clockwise direction, tighteningthe service brake band 29 upon theA drum 25. As the Various brake bandsare suitably lined with a brake lining material, the speed of rotationof the spool 14 may be regulated by the foot lever 40.

A cam 42 is secured upon the shaft 39 at right angles thereto. The cam42 is adapted to bear against the roller 43 on the arm 44. .The arm 44is pivoted at 45 and is pivotally connemed at its opposite. end 46 tothe adjustable connecting member 47, which is adapted to connect the arm44 with the arm 48.

The brake band 32 of the safety brake drum. 26 is pivotally connected ateach end to a bell crank member 49. One end of the brake band 32 towardwhich the drum. rotates in the direction of the arrow as. the cable isbeing wound upon the spool 14, is connected to the bell crank 49-bymeans of a removable pin 50. The other end of the brake band 32 isconnected by the pin 52 to the longer arm of the bell crank 49. The bellcrank 491 is free to pivot at 56 and the bell crank 49 is so designedthat wlien one end thereof holds one end of the band 32 more closelyabout the drum 26, the other end of the band 32. is released somewhat.Owing to the diierence in length of the arms of the bell crank, however,when the bell crank 49 acts to release the end of the band connected bythe pin 5i) a slight amount, the end of the band connected by the pin.52 is tightened a much greater amount. In a similar manner, when thebell crank 49 acts to tighten the end of the band 32 connected bythe pin50 about the drum 26, the other end of the band is released a muchgreater amount.

The adjustable connecting arm 47 extends through the top of the crossmember 12 or through a fixed plate on the frame of the hoist- 80 32 isheld into contact with the drum 26 when all pressure is removed from thefoot lever 40.

A resilient connecting means is interposed between the pin. 52 and theend of the bra-ke band 90 32. A stirrup 56 is pivotally secured by thepin 52. A bolt 57 extends through the lug 58 on the band 32 and extendsslidably through a hole in the base of the stirrup 56. Between the head59 of the bolt 57 and the base of the stirrup 56, 95

is interposed a compression spring 60. The initial tension of thecompression spring 60 is regulated by means of an adjusting nut 62.rl'he bolt 57 is secured in adjusted position to the lug 5.6 by means ofa nut 63. The clockwise rotation 10() of the bell crank 49 is limited bymeans of a screw stop 64 extending through a xed cross member 65 securedto the frame of the hoisting mechanism B.

In the operation oi the hoist, if. no downward pressure: is exerted uponthe lever 40, ythe coinpression spring 54 will cause the brake band 32to contact. slightly ith the brake drum 26 by rotating the bell crank 49in a clockwise direction. It is obvious that a clockwise rotation of 110the bell crank 49 will tend to tighten that end of the band 32 connectedto the lug 58 a much greater distance than will the end of the bandconnected to the pin 50 be released, causing a resultant tightening ofthe band 32. If the spool 14. is rotated in the direction of the arrowor in an anti-clockwise direction, as will be the case when the load isbeing lifted, the bell crank 49 will be pivoted in an anti-clockwisedirection by the actionnof the brake band 32 dragginff upon 120 thebrake drum- 26. Turning the bell crank 49 in. an anti-clockwisedirection acts to release the band 32 andto permit the drum to rotatefreely while the load is being lifted. As soon as the spool 1.4 beginsto rotate in a clockwise direction,

however., the brake band 3,2v will pull on the pin 501 acting to rotatethe bell crank 49 in a clockwise direction. Due tothe diierential actionof the bell crank, the brake band 32 will be tightened about the drum26, preventing the rotation of 13C,

the. spool 14. y

In the operation of the hoisting mechanism B, when the foot lever 40 isdepressed, the cam 42 will bear againsty the roller 43 on they arm 44,

acting through the connecting link or arm 47 to 135 turn the bell crank49 in an anti-clockwise direction.. It is thus. obvious that thedepressing of the foot pedal 40 actsto release the safety brake A. Thefoot lever 40,. however, acts to rotate the arm 38 which is connected tothe movable end or 146 acts: to release the safety brake A and as this1,15

movement isA not` sufficient to tighten the service brake 29, the spool14 may revolve freely in either direction.

The resilienty connection between the pin 52 and the lug 58 onthe end ofthe brake band 32 15G By 85 means of this compression spring 54, theband is for the purpose of preventing tooquick action of the safetybrake A. When a heavy load is being dropped at the time the safety brakeengages the brake drum 26, the strain upon the hoisting mechanism, dueboth to the weight of the load and to the acceleration of the same,might be sufcient to overload some portion of the mechanism. to thebreaking point. The resilient connection between the bell crank 49 andthe lug 58 acts to obviate any danger of such an occurrence.

The compression spring 60 within the stirrup 56 is given an initialcompression by the nut 62, which is sufficient to hold the maximum deadload for which the hoist is designed. When a strain greater than thismaximum dead weight is exerted upon the hoisting cable, the spring 60will compress to a greater extent. The maximum distance to which thespring 60 may compress, is limited by the screw stop 64 which actsagainst one arm of the bell crank 49. When the bell crank 49 is bearingagainst the screw stop 64, the end of the brake band 32 connected to thepin 50 becomes fixed and the maximum action of the brake is limited bythe tension of the spring 69. An extremely heavy load will therefore notcome to a stop with a jerk, as the maximum action of the brake islimited by the compression of the spring 60. The stop 64 is set properlyso that sufficient compression may be obtained in the spring 60 togradually overcome the force of the descending load and the accelerationthereof.

Figure 2 illustrates two spools 14 and 15, each of which are providedwith a service brake and a safety brake. While these brakes for use withthe spool are arranged somewhat differently from the arrangement ofparts used for operating the brakes for the spool 14, these brakesoperate in a similar manner. When the foot lever 66 is depressed, thearm 67 secured on the shaft 68 of this lever will be rotated, actingthrough the links 59 to rotate the arm 70 on the shaft 72. Rotation ofthe shaft '72 produces the same effect as rotating the shaft 39 tooperate both the service brake and the safety brake connected thereto,in the manner which has been described.

Figure 3 illustrates the safety brake A in the Aform which has beendescribed. It may be seen that in this form, the clockwise rotation ofthe bell crank 49 may continue until a certain predetermined compressionof the spring 60 is reached. At this point the further movement of `thebell crank 49 in a clockwise direction is obstructed by the screw stop64. The upper end of the brake band 32, which is connected to the bellcrank 49 by the pin 50, then becomes fixed and the tightness of the band32 about the drum 26 will depend upon the compression of the spring 60.

In Figure 4 is illustrated a similar form of safety brake A. In thisform, however, the bolt 57 is extended through the lug 58 a considerabledistance and through a fixed cross member 73 on the frame of thehoisting mechanism B. In this forno` of safety brake A, the movement ofthe end of the band 32 bearing the lug 58 is limited by the nut 74 onthe bolt 57. As may be seen in this modification, the opposite end ofthe brake band 32 becomes fixed, but it should be noted that in thisform of construction, as well as in the construction illustrated inFigure 3, the pressure on the brake band 32 depends upon the compressionof the spring 69 within the stirrup 56. In practical application, theonly difference between the forms illustrated in Figures 3 and 4, is theconvenience with which the cross members 65 or 73 may be placed in aparticular position. It is also sometimes found that the safety brakehas a tendency to chatter more, when the fixed end of the band 32, whenthe brake is operating under an excessively heavy load, is situated atthe end connected by the pin to the bell crank 49.

A slightly different form of construction embodying the applicantsprinciples of invention is illustrated in Figure 5 of the drawings. Inthis form of construction, the arm 48 does not connect the connectingarm 47 with the shaft of the bell crank 49'. The arm 48 pivots at 75.One end of the brake band 32 is connected tu the arm 48 by the pin 76.The bell crank 49' is pivoted at 77 and one arm 78 of the bell crank 49extends in parallel relationship to the arm 48. An eye bolt member 79 ispivoted at 80 to the arm 78 and extends slidably through a bearing 82 onthe arm 48'. A compression spring 60 is interposed between the bearing82 and a nut 83 on the eye bolt 79. This spring is compressed to themaximum load for which the hoisting mechanism B is designed.

The arm 84 of the bell crank 49 is somewhat longer than the aim 78 andis connected by means of the pin 85 to the lower end of the brake band32. A screw stop 64 extends through a cross member to limit the pivotingof the bell crank 49' in a clockwise direction.

When a greater load than that for which the hoisting mechanism isdesigned, is exerted upon the cable spool, the spring 60 compressesuntil the arm 84 of the bell crank 49 strikes the stop 64. The lower endof the brake band 32 connected by the pin then becomes fixed and thetension of the brake band 32 depends upon the compression of the spring60. It may thus be seen that the form of brake shown in thismodification, acts in identically the same manner as the form of brakeillustrated in Figure 4.

We have described our safety brake in connection with a hoistingmechanism. We wish to have it understood, however, that the applicationof this brake to a hoisting mechanism is only illustrative of one meansof carrying out our invention. The resilient cushioning means shown inthis application may be applied to any mechanism, wherein a differentialbrake is used. While we are aware of the fact that safety brakes havebeen provided heretofore, it is usually found that these brakes actvirtually instantaneously. Brakes of this type would be unsuitable foruse in connection with mechanisms such as hoisting machinery, whereinthe instantaneous stopping of a descending load would place a greatstrain upon the cable and upon the parts of the hoisting machinery.

In accordance with the patent statutes, we have described the principlesof operation of our safety brake, and while we have endeavored to setforth the best embodiment thereof, we desire to have it understood thatthis is only illustrative of a means of carrying out our invention thatobvious changes may be made within the scope of the following claimswithout departing from the spirit of the invention.

We claim:

1. A safety brake for hoisting drum means including, brake means forbraking said drum means, lever means for operating said braking means,safety brake means automatically operated upon the release of said levermeans toward normal position, and means for cushioning the engagement ofsaid safety brake means to overcome shock in braking said drum.

2. A brake for cable spools adapted to control the rotation of the spoolupon which the cable is Wound and unvvound, a brake for stopping saidcable spool, a lever for operating Vsaid brake, a safety brake means,and means for causing said safety brake means to automatically andcushionally engage to stop the spool when said lever is released tonormal position.

3. A brake for cable spools and the like including, means operable byforce exerted upon a lever to stop the spool, and means to cushionallystop the spool automatically upon release of the force exerted upon saidlever and said first means.

4. The combination, spool means for Winding and unwinding a loadsupporting cable, brake means for stopping said spool means, lever meansfor operating said brake means, a safety brake means operableautomatically by the release of said lever means, means for adjustingsaid safety brake to slip under greater than maximum strain, and meansfor releasing said safety brake means simultaneously with the operationof said lever into position to operate said first brake means,

5. The combination, a cable spool for operating a load supporting cable,a service brake for controlling said spool, a safety brake forAemergency operation, means for adjusting said safety brake to slipunder greater than maximum strain, means for operating said servicebrake simultaneously with the release of said safety brake and saidsafety brake with the-release of said service brake.

6. The combination, a rotatable brake drum,

a service brakefor controlling the rotation of said brake drum, a leverfor ,operating said brake, a safety brake operated simultaneously bysaid lever at the releasing of said service brake by said lever,cushioningk braking means on said safety brake, said safety brakeovercoming sudden shock in the application thereof. w

7. The combination, a cable spool, means for operating said spool towind and unwind a load cable thereon, safety brake means forautomatically braking said spool, and resilient cushioning means capableof withstanding maximum load Without operation for overcoming suddenshock to the cablein the operation of said safety brake into brakingposition.

8. The combination, a service brake, a rotatable member controlled bysaid brake, a lever for operating said service brake, a safety brake forsaid rotatable member, cushioning means in said safety brake to overcomesudden shook in the braking application thereof, and means connectingsaid lever in a manner to cause said safety brake to be automaticallyapplied upon the release of said service brake and said safety brake tobe released upon the application of said service brake.

9. A brake for hoisting mechanism including, a service brake, levermeans for controlling said service brake, a safety brake, a cushion insaid safety brake, differential lever means in said safety brake, andmeans connecting said service brake and said safety brake in a manner tocause said brakes to be operated by said single operating lever toautomatically release said service brake Whensaid safety brake isapplied and to automatically release said safety brake when said servicebrake is applied.

10. A brake for hoisting mechanism including, aservice brake, a safetybrake, cushioning means in said brakes, to overcome sudden shock orgrabbing when said brakes are applied, and a single operating controllever for operating said brakes whereby said service brake is operatedby the depression of said lever by the operator against tension, andsaid safety brake is applied automatically by the release of said levertoward normal position.

11. The combination, a rotatable brake drum, safety brake means forautomatically braking said drum, and cushioning means capable ofwithstanding a maximum load in normal brake operation Without beingactuated for overcoming sudden shock in the operation of said safetybrake into braking position.

JOHN R. MCGIFFERT. OLA L. BERBY.

